Switch processes and rapid cycling in bipolar affective disorders, cycloid psychoses and nonsystematic schizophrenia.

Leonhard conceived a hierarchical classification system for endogenous psychoses consisting of a small number of vast, clinically heterogenous main categories. These are subdivided into more homogenous and narrower subcategories: Bipolar affective psychoses, cycloid psychoses and unsystematic schizophrenias are subcategories of a main category of psychopathologically polymorphic, episodic bipolar psychoses. Common features of these related forms of psychoses are syndrome lability, bipolarity and switching. Rapid cycling is a course complication in bipolar affective psychoses as well as in cycloid psychoses and in nonsystematic schizophrenias. Empirically established ideal types of idiopathic psychoses are the foundation of psychiatric classification systems, not only in Leonhard's classification, but also in others. In the description of the features of diagnostic categories based on psychotic ideal types, Leonhard accounted for the low degree of diagnostic specificity of isolated symptoms in so far as he recognised that in bipolar affective psychoses, in cycloid psychoses and in unsystematic schizophrenias intra-episodic syndrome-dynamical features are of greater diagnostic importance. The phenomenon of intra- and interepisodic syndrome lability as a dynamic feature finds its strongest expression in the switch processes.